The present invention relates to a supported catalyst useful for the polymerization of olefins and particularly ethylene under high temperatures and especially under high temperatures and pressures. The invention further relates to the process of polymerizing olefins and particularly ethylene in the presence of the supported catalyst.
The present invention especially relates to the polymerization of ethylene in the presence of the improved supported catalyst at temperatures higher than 150.degree. C. without the need for deashing.
The polymerization of ethylene at high pressure, initiated by a peroxide capable of producing free radicals, has been known and used commercially for many years.
It is, furthermore, known to polymerize ethylene at a low pressure, by using a catalyst of the Ziegler-type, such as, for example, titanium trichloride and an alkyl aluminum compound.
More recently, catalyst components comprising the product obtained by treating a particulate support material, such as silica, with an organomagnesium compound and a transition metal compound and halogen type compounds have been found to be useful for polymerization of olefins under conventional polymerization conditions.
Many of these prior art high-efficiency Ziegler catalysts as described in the plethora of patent literature, have high productivities at a temperature range between 60.degree. and 100.degree. C. However, such high efficiency Ziegler catalysts normally rapidly decay at polymerization temperatures higher than 150.degree. C., and making them unsuitable for use under high pressure, high temperature conditions because of the resulting poor productivity. The prior art high-efficiency Ziegler catalysts also are not especially useful for high pressure-high temperature polymerizations in, for example, a tubular reactor since such catalysts induce plugging and wear in fine tolerance catalyst feeding equipment.
Illustrative of such prior art is a published European Patent Application No. 0052471 assigned to Asahi Kasei Kogyo Kabushiki Kaisha, published European Patent Application Publication No. 0032307 assigned to Imperial Chemical Industries, Limited U.S. Pat. No. 4,173,547 of Graff, issued Nov. 6, 1979, U.K. published Patent Application No. 2068007 assigned to ACC Chemical Company, published U.K. Patent Application No. 2,090,841 assigned to Imperial Chemical Industries and published Australian Patent Application No. 86177/82 assigned to Societe Chim Des Charbonnages S.A. Each of the catalysts disclosed in these patents, although useful for the polymerization at high temperatures, evidence some disadvantages, such as, for example, the large size of the catalyst particles. Large catalyst size is a disadvantage with respect to pumping ease and settling problems at high temperature-pressure polymerizations.
It would be advantageous to develop a catalyst which can be usefully employed for the production of high density polyethylene or linear low-density polyethylene under high temperatures and especially high pressures, which catalyst would combine the properties of high activity, thereby eliminating the need for deashing the polymer product, a short lifetime of about less than 2 minutes, thereby eliminating or reducing the need for quenching agents as the polymer product egresses from the reactor, and the average particle size of the catalyst of less than approximately 7 microns, thereby facilitating catalyst pumping without settling and plugging problems at high pressures and without damaging pump seals.